The present invention relates to a surfactant which has excellent surface activity and safety.
The invention also relates to a detergent with excellent safety, containing the surfactant.
The invention further relates to an emulsion-type cosmetic composition with excellent emulsion stability, safety to skin and sensory properties, containing the surfactant.
A number of compounds are known as surfactants and used in many applications. However, most of those surfactants irritate skin when they are used in cosmetics, such as shampoos, rinses, soaps and other cosmetic compositions, which contact with a human body directly. Therefore, lower irritating surfactants have been desired.
In many emulsions use is made of nonionic surfactants having a polyoxyethylene chain, anionic surfactants such as fatty acid soaps, cationic surfactants or ampholytic surfactants. However, there was a problem that emulsion-type cosmetic compositions with those synthetic surfactants generally tend to irritate skin. Also, even with nonionic surfactants which are said to be less irritating, most of them fit poorly to skin because of their polyoxyethylene chains.
On the other hand, alkylesterified sugars are nonionic surfactants which have been used widely in foods, cosmetics and the like. Among others, sucrose alkylesters in which sucrose constitutes a sugar skeleton are used widely and seen in many publications( Japanese Patent Application Laid Open No. 56-55306/1981). However,those are insufficient in sensory properties and long-term storage stability. Also, it is known to use, as a surfactant, trehalose-6,6xe2x80x2-dialkylester in which a trehalose derivative constitutes a sugar skeleton (Japanese Patent Application Laid Open Nos. 60-258195/1985 and 62-91236/1987). Those are insufficient in emulsifiability.
Synthesis of trehalose fatty acid ester are reported in Chem. Phar. Bull., 30 (4) pp 1169-1174, (1982), where synthesis of 6-stearoyl-trehalose and 6,6xe2x80x2-distearoyl-trehalose and the analysis of them using NMR, etc. are described. Those esters are reported to have anti-tumor activity against Ehrlich ascites tumor in mice. There is no description or suggestion that they show properties as a surfactant. An emulsion-type anti-tumor agent is known in which a specific emulsifier composition is combined with trehalose-6,6xe2x80x2-difatty acid ester as an anti-tumor agent in order to solve a disadvantage that the ester is difficult to dissolve in water (Japanese Patent Application Laid Open No. 61-289038/1986).
In consideration of surface activity, formability, washing ability and so forth for a surfactant, the presence of a single lipophilic moiety is said to be preferred. For example, glucose fatty acid monoester is reported in Japanese Patent Application Laid Open No. 03-157349/1991. However, this has a disadvantage that a stable emulsion can not be obtained due to its weak hydrophilicity.
A purpose of the invention is to provide a surfactant that has excellent surface activity and safety.
Another purpose of the invention is to provide a detergent that has excellent safety.
A further purpose of the invention is to provide an emulsion-type cosmetic that has low irritation to skin, long-term storage stability, excellent sensory properties and beautiful appearance with fine surface texture.
The present invention is a surfactant containing one or more of trehalose-6-fatty acid esters represented by the following formula: 
wherein R represents a saturated or unsaturated acyl group having 8-22 carbon atoms, and may have substituents such as a hydroxyl group.
One preferred embodiment of the invention is a surfactant containing 6-(10-undecylenyl)-trehalose represented by the following formula: 
Another preferred embodiment of the invention is a surfactant containing 6-lauroyl-trehalose.
Further, another preferred embodiment of the invention is a surfactant containing 6-stearoyl-trehalose.
Also, the invention is a detergent characterized in that it contains a surfactant containing one or more of trehalose-6-fatty acid esters represented by the following formula: 
wherein R is a saturated or unsaturated acyl group having 8-22 carbon atoms, and may have substituents such as a hydroxyl group.
Further, the invention is an emulsion-type cosmetic composition characterized in that it contains one or more of trehalose-6-fatty acid esters represented by the following formula: 
wherein R is a saturated or unsaturated acyl group having 8-22 carbon atoms, and may have substituents such as a hydroxyl; and
a water-soluble polymer.
The trehalose-6-fatty acid ester of the invention can be obtained by a condensation reaction of trehalose with a fatty acid or by an ester interchange reaction between trehalose and a fatty acid ester.
Examples of the fatty acid or fatty acid ester which can be used in the invention include synthetic fatty acids and esters thereof, natural fatty acids, such as soybean fatty acid, beef tallow, cotton seed oil, olive oil, palm oil and so forth, and fatty acid esters thereof with lower alkyl groups, which esters are obtained in any conventional method.
Trehalose which can be used in the invention may be xcex1,xcex1-trehalose, xcex1,xcex2-trehalose, xcex2,xcex2-trehalose or mixtures thereof.
The trehalose-6-fatty acid of the invention can be obtained in any usual method of producing sucrose alkyl esters, as described in U.S. Pat. Nos. 2,893,990 and 3,963,699, Japanese Patent Application Laid Openlaid Nos. 36-21717/1961 and 53-6130/1978, all of which are incorporated herein by reference.
The trehalose-6-fatty acid ester is obtained as a main reaction product in these methods. In some cases, there are contained small amounts of unreacted trehalose and trehalose-6,6xe2x80x2-fatty acid diester as a side-reaction product. The trehalose-6-fatty acid ester may be purified in a conventional manner before used, if desired. However, the trehalose-6-fatty acid may be used together with small amounts of unreacted trehalose and trehalose-6,6xe2x80x2-fatty acid diester, because the trehalose-6-fatty acid can exhibit surface activity even in the presence of them.
The trehalose-6-fatty acid ester used in the invention is preferably those in which a fatty acid radical, i.e. an acyl group, has a linear or branched, saturated alkyl or alkenyl group having 8-22 carbon atoms. Examples of those include trehalose monocaprylate, trehalose monononanoate, trehalose monocaprate, trehalose monoundecanoate, trehalose monolaurate, trehalose monomyristate, trehalose monopalmitate, trehalose monostearate, trehalose monoarachidate, trehalose monobehenate, trehalose monoundecylenate, trehalose monooleate, trehalose monolinoleate, trehalose monolinolenate, trehalose monoisostearate, trehalose monohydroxystearate, and trehalose monoricinoleate. One or more from these trehalose-6-fatty acid esters can be used in the invention.
The surfactant of the invention preferably contains one or more selected from 6-(10-undecylenyl)-trehalose, 6-lauroyl-trehalose and 6-stearoyl-trehalose.
The surfactant of the invention has excellent surface activity and safety to skin and also may be used as an emulsifier in foods.
The skin or hair washing agent detergent of the invention preferably contains one or more of the trehalose-6-fatty acid ester in an amount of 1-50 wt. %, particularly 10-35 wt. %. It may further contain other surfactants.
The cosmetic composition of the invention contains one or more of the above trehalose-6-fatty acid ester and a water-soluble polymer. The content of the above trehalose-6-fatty acid ester in the cosmetic composition is preferably 0.01-20 wt. %, particularly 0.1-10 wt. %, based on the total weight of the cosmetic composition. If the content is less than 0.01 wt. %, the emulsion stability of the cosmetic composition tends to decrease during its storage. On the other hand, if it is more than 20 wt. %, it is difficult to obtain fine feeling in use.
The water-soluble polymer used in the invention may be generally any of those used in cosmetic compositions or pharmaceutical bases. Examples of the water-soluble polymer include guar gum, roastbean gum, queensseed, carageenan, galactan, arabic gum, tragacanth, pectin, mannan, starch, xanthan gum, dextrin, succinoglucan, curdlan, gelatin, casein, albumin, collagen, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, methylhydroxypropyl cellulose, soluble starch, carboxymethyl starch, methyl starch, propyleneglycol alginate, salts of alginic acid, polyvinylalcohol, polyvinylpyrrolidone, polyvinylmethylether, carboxyvinyl polymers, sodium polyacrylate, polyethyleneglycol, ethylene oxide/propylene oxide copolymers, cationated cellulose, sodium chondroitin sulfate, and sodium hyaluronate. These water-soluble polymers may be used alone or in combination.
The content of the above water-soluble polymer is preferably 0.001-40 wt. %, particularly 0,01-20 wt. %, on the basis of the total weight of the cosmetic composition. If the content is less than 0.001 wt. %, the emulsion stability of the cosmetic composition tends to decrease during its storage. On the other hand, if it is more than 40 wt. %, it is difficult to obtain fine feeling in use.
The cosmetic composition of the invention may contain one or more oil substances that can usually be used in cosmetic compositions or pharmaceutical bases, if necessary, such as hydrocarbons, such as liquid paraffin, squalane, vaseline and microcrystalline wax; ester oils, such as isopropylmyristate, cetyl-2-ethylhexalate, glyceryl-tri-2-ethylhexanoate, vitamin C palmitate, vitamin C stearate, vitamin C sulfate and vitamin E acetate; waxes, such as beeswax and spermaceti; vegetable oils, such as avocado oil, almond oil, rice bran oil, olive oil, castor oil, rapeseed oil, saffron oil, corn oil, wheat germ oil, soybean oil, cotton-seed oil, tea-seed oil and jojoba oil; animal oils, such as turtle oil, mink oil and yolk oil; higher alcohols, such as cetyl alcohol, stearyl alcohol, oleyl alcohol, octyldodecanol and behenyl alcohol; higher fatty acids, such as laurylic acid, myristic acid, palmitic acid, stearic acid, oleic acid, linolic acid, linolenic acid, ricinoleic acid and isostearic acid; silicone oils, such as dimethylsilicone, methylphenylsilicone and cyclic silicone; other silicone resins and silicone polymers.
The cosmetic composition of the invention may contain polyvalent alcohols, such as ethyleneglycol, propyleneglycol, 1,3-butyleneglycol, dipropyleneglycol, glycerin, and polyglycerins such as diglycerin, triglycerin, tetraglycerin, pentaglycerin and hexaglycerin; trimethylolpropane, 1,2,6-hexatriol, glucose, maltose, maltitol, sucrose, fructose, xylitol, mannitol, sorbitol, maltotriose, threitol, sorbitan, starch-decomposed sugar and starch decompoed reducing alcohol, alone or in combination thereof.
The cosmetic composition of the invention may contain any ingredients customarily used in cosmetics and pharmaceutical bases, such as humectants, active ingredients, fragrances, preservatives, colorants, UV absorbents, astringents, synthetic surfactants, pigments(e.g., kaolin, mica, sericite, talc, yellow iron oxide, red iron oxide and titanium oxide) and water.
The cosmetic composition of the invention includes massage creams, cleansing creams, skin creams, foundation creams, makeup bases, hair creams, massage jellys, and medicinal jellys, but is not limited to those.